1. Technical Field
The present disclosure relates to an organic light-emitting diode display device (OLED), and more particularly, to an OLED that can improve a uniformity of thickness of an organic light-emitting layer.
2. Discussion of the Related Art
Recently, flat display devices, such as a plasma display panel (PDP), a liquid crystal display device (LCD), and an organic light-emitting diode display device (OLED), have been researched. Among the flat display devices, the OLED is a self-luminescent device and can have a thin profile because the OLED does not need a backlight, such as that used for the LCD.
Further, compared with the LCD, the OLED has advantages of excellent viewing angle and contrast ratio, low power consumption, operation in low DC voltage, fast response speed, being strong to resist an external impact because of its solid internal components, and wide operating temperature range. Particularly, because processes of manufacturing the OLED are simple, production cost of the OLED can be reduced more that of the LCD.
FIG. 1 is a plan view illustrating an OLED according to the related art. FIG. 2A is a cross-sectional view taken along line IIa-IIa of FIG. 1. FIG. 2B is a cross-sectional view taken along line IIb-IIb of FIG. 1.
With reference to FIGS. 1 to 2B, the related art OLED includes a substrate 11, including first to third pixel regions P1 to P3 arranged in a horizontal direction, a planarization layer 17 on the substrate 11, a first electrode 20 on the planarization layer 17 and located in each of first to third pixel regions P1 to P3, and a bank 50 covering an edge portion of the first electrode 20 and surrounding each of the first to third pixel regions P1 to P3 on the planarization layer 17. The OLED further includes a power line 13 and a data line 15 in a vertical direction at boundary portions B1 and B2 among the first to third pixel regions P1 to P3, and a gate line 14 crossing the power line 13 and the data line 15 and located at a lower side of the first to third pixel regions P1 to P3. A gate insulating layer 12 is on the substrate 11 covering the gate line 14, and the planarization layer 17 is on the gate insulating layer 12 covering the power line 13 and the data line 15.
When the OLED operates, a driving voltage is supplied to the first to third pixel regions P1 to P3 through one power line 13. Accordingly, the driving voltage drops. Thus, display quality is degraded.
To prevent the driving voltage drop, a width of the first boundary portion B1 between the first and second pixel regions P1 and P2 is greater than that of the second boundary portion B2 between the second and third pixel regions P2 and P3, the power line 13 is arranged on the gate insulating layer 12 at the first boundary portion B1, and the data line 15 is arranged on the gate insulating layer at the second boundary portion B2. Accordingly, a width of the power line 13 becomes great in correspondence to the width of the first boundary portion B1. Thus, even for a large-sized OLED, a driving voltage drop is minimized, and degradation of display quality is prevented.
A width of the bank 50 at the first boundary portion B1 is greater than that of the bank 50 at the second boundary portion B2. Organic light-emitting layers 70a to 70c are formed on respective first pixel electrodes 20. The organic light-emitting layers 70a to 70c are formed using a soluble process method, such as an inject printing method, a nozzle printing method, or the like.
In detail, with reference to FIGS. 2A and 2B, an organic light-emitting material solution is dropped on the first electrode 20 of each of the first to third pixel regions P1 to P3, then the dropped organic light-emitting material solution is dried. Thus, the organic light-emitting layers 70a to 70c are formed. In this case, the width of the bank 50 at the first boundary portion B1 is greater than that of the bank 50 at the second boundary portion B2.
Accordingly, for the dropped organic light-emitting material solution in each of the first to third pixel regions P1 to P3, an evaporation environment of solvent molecules of the organic light-emitting material solutions located at respective sides of the first and second pixel regions P1 and P2 with the first boundary portion B1 therebetween is different from an evaporation environment of solvent molecules of the organic light-emitting material solutions located at respective sides of the second and third pixel regions P2 and P3 with the second boundary portion B2.
In other words, when drying the organic light-emitting material solutions, an evaporation rate of the solvent molecules of the organic light-emitting material solutions located at adjacent sides of the first and second pixel regions P1 and P2 is faster than an evaporation rate of the solvent molecules of the organic light-emitting material solutions located at adjacent sides of the second and third pixel regions P2 and P3.
Accordingly, after drying the organic light-emitting material solutions, unlike the organic light-emitting layer 70c formed in the third pixel region P3, the organic light-emitting layers 70a and 70b formed in the first and second pixel regions P1 and P2 become thicker where they are closer to the first boundary portion B1. Such non-uniformity of thickness of the organic light-emitting layers 70a to 70c causes degradation of display quality of the OLED and reduction of light emission efficiency and lifetime of the OLED.